The invention relates to an oxidation furnace for the oxidative treatment of fibres, particularly for producing carbon fibres, having    a) a housing which is gastight apart from inlet and outlet regions for the fibres;    b) a process chamber located in the interior of the housing;    c) a blowing device by means of which hot air can be blown into the process chamber;    d) at least one suction device which is arranged in an end region of the process chamber, extracts hot air from the process chamber and comprises a plurality of suction boxes which are arranged at a vertical spacing from one another and have at least one outlet opening for the hot air and, on one side, at least one inlet opening for the hot air, which communicates with the process chamber;    e) at least one ventilator which circulates the hot air through the blowing device, the process chamber and the suction device;    f) at least one heating device located in the flow path of the hot circulated air;    g) guide rollers which guide the fibres in serpentine manner through the clearances between suction boxes located above one another.
There are various ways of conducting the hot air for treating fibres through an oxidation furnace. The flow direction can be aligned transversely, vertically or even horizontally to the direction of the fibres here. Oxidation furnaces which conduct the air according to the “centre-to-end” principle are gaining increasing acceptance. In this, the hot air is blown out in the central region of the process chamber in both directions, that is in the direction of the opposite ends of the process chamber, and extracted again by suction devices at these two ends of the process chamber. The description below refers to “centre-to-end” air conduction by way of example, although the invention is not restricted to this.
The process chamber can also be seen as a zone which is repeated in the longitudinal direction of the furnace for different temperatures and air flows.
In known oxidation furnaces of the type mentioned at the outset, the suction openings of the suction boxes which communicate with the process chamber are located on that side which faces the centre of the process chamber. As a result, hot air no longer flows through the clearances between the suction boxes, at least not to any notable extent. Therefore, the paths covered by the fibres between the suction boxes are not used for the oxidative treatment. Since the suction boxes need to have considerable dimensions owing to the air distribution, the stretches in which there is no oxidative treatment of the fibres due to a lack of air flow are by no means insignificant.